U.S. Pat. No. 1,634,843 issued in 1927 to McWane, discloses a window guard having a plurality of horizontal rods 11 interconnecting two opposite lateral studs 7, 8. Studs 8 include transverse bores 9, while stud 7 includes transverse notches 13. Core extensions 10, 14, of each rod 11 at opposite ends thereof engage a corresponding bore 9 and a notch 13, respectively in studs 8, 7. A lock bar 16 is slidably mounted in the hollow notched stud 7, for releasably locking (with integral transverse pin 17) the rod core extension 14 in position against unauthorized egress from the notch 13.
The flaw in the McWane device is clear: the burglar needs only to break the glass of the window pane, to access the lock bar 16 and release the rods 11 from the studs 7, 8. This is not safe.
U.S. Pat. No. 4,395,861 issued on Aug. 3, 1983 to Fipke and Oswald, constitutes an improvement in two ways. First, the transverse window bars 4 include a central cylindrical metallic core 8 (FIG. 2) which is freely rotatable within the tube 4, so that any attempt at sawing the core 8 will bias the latter to rotate in the direction of sawing, thus in effect preventing effective sawing action (since there is no real grip of the saw teeth on the surface of the rod which surface moves with the saw blade during sawing motion). Second, the lock bar 15 (FIGS. 6 and 9), which releasably locks the ends of rods 4 into notched stud 4, is controlled by a stem 19 extending inwardly through the building wall 17. In its operative position, stem 19 prevents egress of the corresponding ends of rods 4 from the notches 14 (FIG. 7) of stud 2. Stem 19 is actuatable solely by a handle 21 located inside the building, at a distance from the window aperture, so that even if the window pane is shattered by a burglar, unauthorized access (from outside of the building) to the window guard release handle 21 will be denied.
Unfortunately with these known prior art window guards, the overall weight (transport costs) and manufacturing cost tend to be relatively high. Since these features are critical in this intensively competitive market, they do have an impact on projected sales. Studies have shown that current window guards (either of the grid type, or of the adjustable bar length type) tend to be considered as unaesthetic (customers complain of being like inside a prison).
It is understood that all window guards are now required by law to be releasable from the inside, so as to constitute an escape passageway in case of fire inside the building.